Hydrofoil stabilizing means for watercraft



Nov. 22, 1966 H. w. NASON HYDROFOIL STABILIZING MEANS FOR WATERCRAFTFiled June 21, 96

5 Sheets-Sheet 1 Nov. 22, 1966 H. w. NASON HYDROFOIL STABILIZING MEANSFOR WATERCRAFT 5 Sheets-Sheet 2 Filed June 21, 1965 Nov. 22, 1966 H. w.NASON HYDROFOIL STABILIZING MEANS FOR WATERCRAFT 13 Sheets-Sheet 5 FiledJune 21, 1965 United States Patent 3,286,673 HYDROFOIL STABILIZING MEANSFOR WATERCRAFT Henry W. Nason, 366 Farmington Ave., Plainville, Conn.Filed June 21, 1965, Ser. No. 465,371 15 Claims. (Cl. 114-665) Thisinvention relates in general to stabilization devices for watercraftmoving in a body of water and, more particularly, the invention isconcerned with .a hydrofoil type of stabilizing apparatus for sailingcraft, motor driven boats, and other watercraft.

Various problems are encountered in providing for stabilization ofwatercraft moving in a body of water, particularly where the surface ofthe water may be affected by wind and storms and other conditions. Awatercraft may be regarded as a rigid body with three degrees ofrotational freedom, namely roll, pitch, and yaw and three degrees oftranslational freedom herein designated as forward, lateral and verticaldisplacements. A stabilizing control system for limiting selectedcomponents of such motion should meet three basic requirements. First,the displacement -to be controlled should be sensed. Secondly, a forceof moment is required to be generated to balance any disturbing force ormoment tending to drive the sensed displacement from its normal ordesired value. Third, the control system must be statically anddynamically-stable under the influence of the expected disturbances ordisplacements.

For sailing craft the desired value of roll is generally zero formaximum sail effectiveness, mini-mum hull drag and comfort. The pitchmust be constrained to follow the general water surface profile forsuccessful wave contouring. Yaw is usually allowed to be completely freefor directional control under the influence of rudder forces.

A driving force must be provided to move the watercraft forward. Inregard to sailing craft as opposed to mechanically powered boats, alateral force is necessary to control leeway or slip downwind. For theminimization of bull drag it is desirable to reduce the wetted area andthus height stabilization or vertical positional control isadvantageous.

It is, therefore, a chief object of the invention to provide improvedstabilization means for controlling travel -of a watercraft on a bodyofwater and, more particularly,

it 'is an object of the invention to devise a stabilizing apparatuswhich can be practically combined with sailing craft to quickly sensethe action of force causing a change in position; which can generate anopposed balancing system of forces; and which can be made statically anddynamically stable in a sail boat environment.

With these general objectives in mind, and having regard for theproblems indicated, I have devised a unique and novel arrangement ofstabilization control components for use with a watercraft andparticularly a watercraft of the sail boat class. The stabilizationcontrol apparatus of the invention is based on the concept of combiningwith the watercraft specially supported float members and hydrofoilmeans mechanically linked to the float members in a unique manner.

The novel concept of the invention is based on a recognition of the factthat a sailing craft equipped with side float members movably connectedto rigid transverse supporting members in a manner which constrains thefloats to translate with limited rotation relative to the watercraft ina vertical plane essentially parallel to a vertical plane determined bythe sailing craft mast and longitudinal axis will sense roll and heightvariations of the sailing craft by motion of the floats in this plane.The fact has been further combined with realization of the ice large"hydrodynamic forces which may be developed on the sailing craft by asystem of fully submerged controllable hydrofoil members. An importantfeature of this novel arrangement of parts 'is that the severalcomponents are so organized and interconnected to one another as toprovide an automatic all mechanical feedback control system forgenerating and applying forces acting in opposed relationship todisturbance forces in order to limit roll and other changes in positionof the sailing craft.

It is another specific object of the invention therefore to utilize thecombined effects of float members and hydrofoil components incombination with supporting arms of relatively short length solidlyanchored to the upper side of the deck of the sailing craft so that theycan be permanently maintained at these points.

It is a further object of the invention to achieve multiple use ofvertical hydrofoil supporting struts by utilizing the struts as daggerboards to resist leeway as Well as functioning to maintain adjustablehydrofoils submerged in water. Still another object is to provide anarrangement of hydrofoil units which permits the hydrofoils and theirsupporting struts to be .easily rotated out of the water in a rearwardand upward manner for purposes of reducing drag forces at low speedswhen the hydrofoils are ineffective, for beaching, or for safety whenstriking underwater objects.

Still another object is to arrange the mechanism to allow the movablefloats to be fixedly positioned and for the controllable hydrofoils tobe simultaneously set at an incidence yielding minimum lift and yetallowing the hydrofoil units to be rotated either into or out of thewater with essentially no further incidence change.

Still another object is to construct an apparatus in which the size ofthe outrigger floats i reduced relative to conventional sizes of suchdevices and to fixedly position the floats so that they may be used inaconventional manner at low speeds whenthe hydrofoils are lifted and maybe utilized as movable roll and height reference members at higherspeeds when the hydrofoils are immersed and operative.

Still another object i to provide a design of a relatively deep narrowbeam type hull to minimize drag and to furnish a suitable degree ofleeway resistance when the hydrofoils are lifted in light wind and tofurther .provide for a successful wave contour in heavy seas when thehydrofoils are down and the hull is partially orcompletely lifted out ofwater.

The nature of the invention and its other objects and novel featureswill be more fully understood and appreciated from the followingdescription of preferred embodiments of the invention shown in theaccompanying drawing in which:

FIGURE 1 is a perspective view of a' sailing craft with which thestabilizing means of the invention is combined;

FIGURE 2 is a rear elevational View of the sailing craft of FIGURE 1 butfurther indicating the sailing craft diagrammatically in a body of waterand showing float and hydrofoil components of the invention in a typicaloperative position in the body of water;

FIGURE 3 is a plan view indicating diagrammatically the sailing craftand the stabilizing means of the invention attached thereto;

FIGURE 4 is a side elevational view of one of the float members of theinvention, together with portion of float supporting spars shown removedfrom the sailing craft;

FIGURE 5 is a perspective view further showing details of the controlrod means for connecting a hydrofoil element with a float pull arm;

FIGURE 6 is a detail fragmentary perspective view illustrating lockingmeans for maintaining a float member and hydrofoil element in onedesired position and for varying a hydrofoil control rod to carry out avertical displacement trim adjustment.

FIGURE 7 is a side elevational view of a float member and furtherillustrates a hydrofoil assembly including vertical spaced struts andhydrofoil elements supported between the struts in an operativeposition;

FIGURE 8 is a detail fragmentary side elevational view showing means forholding the hydrofoil assembly in a raised position;

FIGURE 9 is a side elevational view showing the hydrofoil assembly in araised position relative to the float member;

FIGURE 10 is a view illustrating a truss arrangement for supporting thestabilizing means of the invention; and

FIGURE 11 is a view showing another modification of the invention.

The principal parts of the invention include a pair of float membersconnected by hinged pull arms to float supporting spars adapted to betransversely secured in parallel spaced relation at the upper side of awatercraft. Operativelyconnected to each of the floats through thehinged pull arms by means of suitable linkages are two hydrofoil units.These hydrofoil units are also secured to a hydrofoil supporting sparpivotally mounted at the upper side of the watercraft between the floatsupporting spars.

Considering these parts in greater detail, attention is directed toFIGURES l to 3 inclusive wherein numeral 1 denotes the hull of aWatercraft which may, for example, be of the sail boat class having amast 2 and a boom 3. A sail 4 is attached to the mast and boom. Numeral5 denotes a rudder operated by means of a tiller 5'. The invention willbe described with specific'reference to stabilizing a sail boat althoughit should be understood that this is not done in any limiting sense.

In accordance with the invention, I provide two float members 9 and 9which preferably consist of water-tight buoyant members made in theboat-like shape shown in the drawings. I further provide for locatingthe float members at either side of the hull in spaced relation theretoand in a position such that they may normally rest in the body of waterW in which the watercraft is floating as indicated diagrammatically inFIGURE 2.

It is an essential feature of the invention that the floats be attachedthrough a part rigidly connected to the hull in some desired manner. Asone suitable means of locating the float members 9 and 9 in the positiondescribed and shown, I may employ float supporting spars 6 and 8 whichare solidly secured at the upper side of the watercraft and which extendtransversely thereof in parallel spaced apart relation. Preferably thefloat supporting spars may be arranged at points forward and aft of thecockpit area of the watercraft 1 as suggested in FIGURE 1.

An important feature of the invention consists in the manner in whichthe floats are attached to the rigid float supporting spars 6 and 8 andattention is directed to FIG- URES 3, 4, 5 and 6 wherein I haveillustrated pull arms 12, 12 and 13, 13'. The pull arms are pivotallyconnected at their upper ends to respective extremities of floatsupporting spars 6 and 8 in the manner more clearly shown, for example,in FIGURES 5 and 6. The lower ends of the pull arms are similarlyconnected to the floats 9 and 9. The connecting pivot means may in onedesirable form consist in hinge members as 14, 15, 16 and 17.

It will be understood that other type devices than hinges may beemployed for the pivotal attachment desired between supporting spar endsand each extremity of the pull arms. However, it is essential thatwhatever type of pivot means is employed, it be so chosen as to providefor the establishment of a parallelogram of pivot axes 14, 15, 16, 17and 14', 15', 16' and 17 which constrain the floats 9 and 9' totranslate only in a plane essentially parallel to a plane determined bythe mast 2 and the longitudinal 4 axes of the watercraft 1. The effectof this is that the longitudinal axes of the floats 9 and 9' areconstantly maintained at a fixed angle relative to the longitudinal axisof the watercraft 1 and movement of the floats in this parallelrelationship has been indicated in the drawings by arrows U and D forexample in FIGURE 1.

Considering next the hydrofoil units and associated linkages earlierreferred to as being operatively connected to the float pull arms,attention is again directed to FIG- URES l and 2. In the latter figure,I have illustrated the two hydrofoil units H1 and H2, and in FIGURE 1the hydrofoil unit H1 is shown on a somewhat exaggerated scale. It willbe understood that the specific sizes and shapes shown may be varied indifferent ways and the invention is not intended to be limited to theproportions or sizes illustrated in the drawings.

The hydrofoil units, as was the case with the floats earlier described,are required to be attached to a part which can be rigidly held in or onthe hull of the boat 1 in an operative position. For this purpose I may,as suggested in FIGURE 1, provide a hydrofoil supporting spar 7 which ismounted at the upper side of the watercraft preferably by means of somesuitable pivot means as, for example, hinges 7b and 70 (FIGURE 3) inclose proximity to the float supporting spar 6 and in parallelrelationship therewith.

An operating handle 7d is attached centrally of the supporting spar andprojects rearwardly as shown in FIG- URES 1 and 3 in a position to allowan occupant in the cockpit area of the boat to rotate the supportingspar 7 into a position such as that shown in FIGURE 8 in dotted lines.In the dotted line position a fastening part 7e may be engaged with alocking rod 7 to hold the handle 7b in the raised dotted position whendesired.

To secure the operating handle 70! together with the spar 7 in a fixedlowered position, I further provide a fastening 32 which can be anywell-known type of clamping device anchored to the boat and adapted tooverlie and adjustably secure the handle as shown.

The hydrofoil supporting spar mounted as described is in accordance withthe invention, employed to locate the hydrofoil units H1 and H2 innormally vertically disposed positions in the water W preferably outsideof the floats 9 and 9 as may be more clearly seen from an inspectionofFIGURE 2. Each of the two units H1 and H2 are similar in constructionand similar parts are indicated by similar but primed numerals.

Considering the unit H1, numeral 11 refers to a hydrofoil element whichis pivotally supported between two vertical strut components 10 and 10aand positioned by a control linkage hereinafter described. The hydrofoil11 is constructed of a shape to provide a wing-like surface which, whenmoved through the water W, develops forces whose direction and magnitudedepend upon the speed of motion and the angular position of thehydrofoil with respect to the direction of movement in the well-knownmanner. The configuration of the hydrofoil 11 in one desired form hasbeen indicated on a somewhat enlarged scale in FIGURE 5 and it should beunderstood that other shapes and proportions may be employed.

The stuts as 10 and 10a may be secured to the hydrofoil supporting spar7 in any desired manner and in one specific instance the struts may beformed with slotted portions through which the ends of supporting spar 7is received as shown in FIGURE 5. To provide for pivotal mounting ofhydrofoil 11, I have employed pins P and P1 which are transverselymounted in a suitable bearing portion in the respective struts as shownin FIGURE 2. Other pivot arrangements may also be employed.

It is contemplated that the hydrofoil supporting spar 7, together withthe attached hydrofoil units H1 and H2, will locate the hydrofoil unitsin a substantially vertically disposed position in the body of water W,and when the fastening part 32 is engaged this position will normally bemaintained with the boat in motion.

aasaevs An important feature of the invention consists in operatingcontrol linkages for the hydrofoils 11 and 11. The operating controllinkage basically involves connecting the hydrofoil elements torespective float pull arms in such a way that change inposition of thepull arms will result in varying the position of angularity ofrespective hydrofoil elements and the linkage is further constructedsuch that a trim adjustment may be realized between the pull arms andrespective hydrofoil elements. Considering the operating linkage for thehydrofoil 11, there is provided on the front portion of the hydrofoil anincidence control arm 22. This incidence control arm 22 is pivotallyconnected to a vertical control arm '20 in turn pivotally connected to atransverse control arm 19 adjustably secured in the pull arm 12 in anadjustment mounting 36. It will be understood the hydrofoil 11 isconnected to a similar linkage attached to the pull arm 13 by means ofthe operating linkage described. It will be apparent that movement of apull arm about its axis of pivoting will cause the vertical control rod20 to move up and down and vary the position in which the hydrofoil 11may be located at any given time when immersed in water. Considering theoperation of the mechanism described, if the sailing craft in FIGURE 1is in motion and is rolled in the direction of the arrow R the float'9'will fall in the direction of the arrow D causing a downward motionof the pull arms 1-2 and '1-2' and vertical control rod 20 in thedirection of the arrow F. This downward motion of the control rod 20causesthe hydrofoil 11 to be deflected in the direction of the arrow Bthus causing a hydrodynamic force which opposes displacement in thedirection of the arrow R.

From symmetry considerations it will be apparent that :the starboardfloat 9' and associated hydrofoil 11' will deflect in an oppositedirection to the port float 9 and hydrofoil 11. This differential motionof the two hydrofoils due to roll R or L :is additive in respect to thegeneration of opposing roll moments on the main hull 1 transmitted byway of the struts '10, 10a, 10', 10a and hydrofoil supporting spar 7. Itwill be noted that the spar 7 is secured to the main hull 1 ahead of thesailing crafts center of gravity.

Next assume that the main hull 1 again has forward velocity and is movedvertically in the direction of the arrow H. Both floats 9 and 9' willfall in the direction of the arrow D which causes a downward deflectionof :the associated hydrofoils 11 and 11' and results in a decrease intheir 'lift. This decrease in lift of the hydrofoils 1 1 and 11' causesthe main hull 1 to be accelerated in the direction of the arrow I thusopposing the original motion H. Depending upon 'the size of the forcecausing .the initial vertical movement H, the pull arm lengths anddepression angles, the proportionality constant of the linkage made upof the vertical control rod, pivot armand incidence control arm, and thehydrofoil effectiveness, the main hull 1 will seek a change in height"relative to 'the'nominal stabilizedheight.

The apparatus of the invention further provides for adjustment of thenominal stabilized height of the -boat. This is achieved by a mechanicaltrim adjustment of the position of the transverse control arm 19 on thepull arm 12 as illustrated in FIGURES 5 and 6. Positioning of thetransverse control arm 19 is accomplished by an adjustment arm 36pivotally secured to the forward vpull arm 12 at point 35. The pivotaxis 35 is parallel to the hinge axis 14. A slotted bar 37 attached tothe adjustment trim arm 36 is secured to the pull arm 12 by anadjustment knob 38. For sailing craft this nominal stabilized heightwould be designed to only partially lift the main hull out of the waterto compromise decreased hull resistance and safety. A narrow beam deep Vcross-sectional main hull is thought to be desirable both from aperformance .and construction standpoint.

When the apparatus of the invention is utilized to lift the main hull ofthe sailing craft out of the water to a degree wherein the inherentpitch stability due to force and aft buoyance variations on the mainhull is lost, a rear fixed incidence hydrofoil 11a becomes necessary asshown in FIGURES l and 2. It is optional otherwise. A mechanicallypowered craft with a deep V cross-section for its main hull, which ismaintained in a controlled manner at a predetermined height eitherpartially below or slightly above the average level of small amplitudewaves (less than approximately 1 foot), is capable of negotiating bycountouring (following general wave profile) much larger wavesencountered in severe seas.

Although the function of the roll and height stabilization features havebeen described in a step by step fashion and separately, it will beunderstood that in practice these occur simultaneously andinstantaneously subject to the time lags associated with the damping andinertia characteristics of the system.

In addition, to the two primary effects of roll and height sensing andstabilization, there are some secondary effects which are believed 'tobe evident from the foregoing disclosure. Assuming that the watercrafthas gained forward momentum, a rearward drag force acts on each float 9and '9. This drag force creates an unbalanced moment about the upperhinge axes 14 and 16 tendingto lift both floats out of the water in thedirection 'ofthe arrow U (FIGURE 1). As the 'two floats lift there is acorresponding decrease in the upward buoyant force .of the water on thefloats.

Since a component of the drag force is aiding the buoyant force whichbalances the float weight, the imntediate result is to rotate the floatsupward and hence yield an upward angular rotation of the forward pullarms which is a function of the boat velocity and tending to increase asthe boat velocity is increased.

Upward rotation of the pull arms causes each hydrofoil to be alsodeflected upward, which increases the :lift coeflicient and transmits alift force to the hydrofoil supporting spar 7 and the main hull. Thislift force causes the main hull 'to rise which'in turn causes a downwarddeflection of the foils partially cancelling the up- ;ward deflection ofthe foils due to the original drag force. The total effect of the dragis thus a steady upward defleclfiOn of the hydrofoils, a steady upwardlift force transmitted to the main hull and a decreased displacement ofthe main hull.

For a sailing craft which is so designed to achieve rpitch stabilityonly from fore and aft buoyancy change .in the 'main hull (no fixedincidence rear foil) then this drag induced hydrofoil lift force ishighly beneficial. This is explained as follows. Sincethe hydrofoil supporting spar 7 is located forward of the center of gravity of the crafta pitching moment is generated in a direction to lift the bow out of thewater. This moment is :caused 'by the hydrofoil lift induced by thehydrodynamic drag force on the floats and thus increases in magnitudewith increase in boat velocity through the water.

Since the sails produce a pitching moment tending to push the bow downand such a moment tends to increase with wind velocity and thus boatvelocity, this secondary float drag effect opposes the sail pitch effectand is thus a favorable and highly desirable stabilizing phenomena ofthis invention. Recognition of the fact must be made that the techniqueof attaching the floats 9 on the pull arms 12 and 13 by the hinges 14,1'5, 16 and 17, actually prevents the floats from responding to smallamplitude pitching oscillations of the main hull 1. Consequently, thisdrag induced lift and pitching moment will not fluctuate due to pitchingoscillation of the craft and 'hence will be a relatively steadyingstabilizing moment as is the destabilizing pitching moment of the sailsduring small amplitude pitching motion relative to the water surface.

The floats 9 in calm water at zero boat velocity seek a static positionon the water determined by the balance of their buoyant force and weightdue to gravity. However, in disturbed water and at boat velocities otherthan zero, the floats position will be perturbed by surface waves andinertial reaction forces on the hinges 15 and 17 due to roll and heightacceleration of the main hull. The floats consequently are designed tohave a length of at least one-half to approximately two-thirds thelength of the main hull. Therefore small wave disturbances will befiltered out naturally.

I may also provide, as an aid to dampen this perturbed motion, fixedfiins 24, 24' which may be added to the floats 9 and 9' at a positionbelow the normal water line of said floats. With this arrangement anyvertical velocity of the floats relative to the water surface willresult in an angle of attack variation of these fixed fins in such adirection to generate a force on said fins that opposes this verticalvelocity.

The fixed fins 24, 24' can also be arranged to serve another function.By setting their fixed angle of incidence at a value other than at zero,then an upward or downward hydrodynamic force can be created which isdependent on boat velocity, and which will force the floats to seek aposition above or below their normal floating position at zero speed. Bydesign this hydrodynamic lift force can be made to aid or counteract thedrag forces on the floats which in all cases causes the floats andassociated hydrofoils to generate more lift.

It is, of course, undesirable in the case of a sailing craft to have thefin force counteract completely the drag force, which always lifts thefloat higher in the water, since this would result in losing the bow-uppitching moment on the main hull as previously discussed.

As a further aid in damping the coupled watercraft and float motion arate damper 42 may be used shown attached to the float 9 at point 44 andthe rear pull arm 12' at point 43. Motion of the floats 9 and 9'relative to the watercraft 1 will be damped by this device and its formcan be any well-known type of dash-pot damper.

Means have been provided in the apparatus of the invention for limitingthe angular deflection of the hydrofoils 11, 11' to prevent rotationbeyond their normal design range which would be less than the stalledcondition. Referring to FIGURE 4 showing a side view of float pull armand hinge means, bolts as 25, 25' have been rigidly attached to the topsurface of the float 9 at points forward of the hinge axes 15 and 17.The bolts 25, 25 pass through holes as 26, 26' in the pull arms 12 and12' and the bolts have adjustment nuts 27, 27' and lock nuts 28, 28'that limit the angular motion of the pull arms with respect to thefloats.

By means of the action of the arms 19, 20, 22 and the hinges 14, 15, 16and 17 previously discussed, and by limiting the angular motion of thepull arms 12 and 12' relative to the float, there is accomplished alimitation of the angular deflection of the hydrofoils.

The floats 9, 9' are by design able to effectively counteract heelingmoments due to sail forces in light breezes by virtue of their weightand/ or buoyance alone. Thus provision has been made to simultaneouslylift the hydrofoil units H1 and H2 out of the water and to temporarilysecure the pull arms 12 and 13 against rotation from a chosen position.These effects are derived by employing the handle 7d to rotate thesupporting spar 7 upwardly as earlier described.

When the hydrofoil supporting spar 7 is rotated in the direction of thearrow G the struts and hydrofoils move rearward and upwardly since thestruts are rigidly attached to the spar 7 and the hydrofoils arepivotally attached to the struts. This rotation should be made with aminimum of force requirements on the handle 7d for it must beaccomplished by a single operator for a reasonable sized sailing craft.

As an aid in minimizing this handle force a locking bar 39 is made toengage the transverse control arm 19 in a slot 41 by a rearward motion Iof the locking bar 39 in the sleeve 40 as shown on FIGURE 6. This notonly fixes the forward pull arm 12 and float 9 but sets the hydrofoilelement 11 at an incidence chosen to yield minimum hydrodynamic lift andthus minimizes the force transmitted to the handle 7d by way of thestruts and hydrofoil supporting spar. The normal operating sequencewould be to engage the transverse control arm 19 with the locking bar 39prior to releasing the fastening 32.

Since the hinging axes 7b, P, and the pivotally mounted end points ofthe vertical control rod 20 form essentially a parallelogram, then therewill be a minimum of angular change of the hydrofoil element 11 relativeto the watercraft when the hydrofoil supporting spar 7 is rotated in thedirection of the arrow G as illustrated in FIGURES 7, 8 and 9. Thiseffect further contributes to the minimization of the force exerted onthe handle 7d by the operator and allows the hydrofoil units H1 and H2to be either lowered into or retracted from the water while thewatercraft is underway.

With the hydrofoil units retracted from the water and with the floats 9and 9' fixed relative to the watercraft then the boat functions in amanner identical to a conventional double outrigger canoe. The fastening32 may be designed to break or release at a predetermined load as asafety feature when a strut or hydrfoil strikes a floating or submergedobject. The rearward and upward motion of the hydrofoil units after thefastening 32 is broken or released is in the proper direction tominimize further damage after the first impact with the floating orsubmerged object. The ability to lift the hydrofoil units is a usefulfeature for launching the sailing craft from shallow beaches.

FIGURE 10 illustrates a truss arrangement of supporting the mast 2, theforward float supporting spar 6, and hydrofoil supporting spar 7, andincludes angularly disposed truss members T1, T2, T3, T4, T5. By theutilization of such an arrangement of truss elements it is possible todecrease the structural loads sustained by the main hull 1 and wouldtend to allow the construction of a lighter main hull 1.

FIGURE 11 shows a modification of the major components of the apparatus.The hydrofoil supporting spar 7 is moved forward of the float supportingspar 6" and the forward pull arm 12" is extended forward beyond thehinge axis 14" to actuate the vertical control rod 20". This allows therod 20" to be placed aft of the struct 10" axis and is thus in a lessvulnerable position. The vertical control rod 20" can, of course, beenclosed within tlhe aldljacent strut in either the arrangement ofFIGURE Although in the foregoing description I have illustratedpreferred embodiments of the present invention, other modifications maybe employed. The floats 9 may be placed either between or outboard ofthe struts 10 and may be constrained to translate in only the verticaldimens1ons, for example, by means of fixed bearings and slides. Inaddition the floats may be allowed to translate 111 two dimensions withlimited movement relative to the watercraft.

In the specification the term substantially vertical as applied inreference to the disposition of the hydrofoil units is intended toinclude some deviations of from 20 to 30 or more. I

These and other changes and modifications may be resorted to in keepingwith the scope of the appended claims.

I claim:

1. An apparatus of the class described comprising in combination awatercraft supported in a body of water, float supporting means solidlysecured to the watercraft and projecting transversely outwardly fromeither side thereof, a pair of float members, pull arms projectingdownwardly and rearwardly relative to the float supportig means, saidpull arms hingedly connecting the float members to the float supportingmeans in spaced relation to the watercraft in said water and hydrofoilmeans independently connected to the watercraft and including hydrofoilelements operatively connected to the pull arms and movable therewith.

2. A structure according to claim 1 in which the float supporting meansincludes a pair of rigid spars occurring in spaced apart parallelrelation at forward and rearward parts of the watercraft and saidhingedly connected pull arms including hinge elements for connectingupper extremities of the pull arms to the rigid spars and for connectinglower extremities of the pull arms to respective floats to provide fouraxes of hinging at the lower ends of the pull arms which coincide withthe points of intersection of four sides of a parallelogram.

3. A structure as defined in claim 1 in which the hydrofoil meansincludes a hydrofoil supporting spar transversely secured to thewatercraft in parallel relation with the float supporting means and apair of hydrfoil units suspended at opposite ends of the hydrofoilsupporting spar in spaced relationship to the said float means andextending into the said body of water at points below the float means.

4. A structure as defined in claim 1 in which the hydrofoil meansincludes a hydrofoil supporting spar transversely secured to thewatercraft in parallel relation with the float supporting means and apair of hydrofoil units suspended at opposite ends of the hydrofoilsupporting spar in spaced relationship to the said float means andextending into the said body of water at points below the float means,each of said hydrofoil units including a pair of vertically disposedstruts spaced apart and having a hydrofoil element pivotally supportedtherebetween and connecting linkages extending between each of thehydrofoil elements and a respective pull arm of the floats.

5. A structure as defined in claim 1 in which the hydrofoil meansincludes a hydrofoil supporting spar transversely secured to thewatercraft in parallel relation with the float supporting means and apair of hydrofoil units sus pended at opposite ends of the hydrofoilsupporting spar in spaced relationship to the said float means andextending into the said body of water at points below the float means,each of said hydrofoil units including a pair of vertically disposedstruts spaced apart and having a hydrofoil element pivotally supportedtherebetween and connecting linkages extending between each of thehydrofoil elements and a respective pull arm of the floats, the saidconnecting linkages including an incidence control rod attached to aforward edge of a hydrofoil element, a vertical control rod pivotallyconnected to the incidence control rod and a pull arm actuated controlrod adjustably secured to the pull arm and pivotally pinned to thevertical control rod whereby a rotative movement of a pull arm maychange the position of angularity of the hydrofoil element.

6. A structure as defined in claim 1 in which the hydrofoil meansincludes a hydrofoil supporting spar transversely secured to thewatercraft in parallel relation with the float supporting means and apair of hydrofoil units suspended at opposite ends of the hydrofoilsupporting spar in spaced relationship to the said float means andextending into the said body of water at points below the float means,each of said hydrofoil units including vertically disposed strut meanshaving a hydrofoil element pivotally supported thereon and connectinglinkages extending between each of the hydrofoil elements and arespective pull arm of the floats and each of said linkages including anincidence control arm attached to a hydrofoil element, a verticalcontrol arm pivotally pinned to the incidence control arm and means forconnecting the upper end of the vertical control arm to a respectivepull arm pivot mecha- It) nism, and said pull arm pivot mechanism beingadaptedto secure the vertical control rod 'in varying positions ofadjustment to provide a trim adjustment for the hydrofoils.

7. A stabilizing apparatus for a boat supported in a body of watercomprising a pair of float members, float supporting spars fixed to theupper 'side of the boat in parallel spaced relation and projectingoutwardly attwo opposite sides, pull arms extending rearwardlyanddownwardly between the floats and adjacent extremities of the floatsupporting arms to locate'the float members in the body of-water, meansfor connecting the floats to respective spar extremities in hingedrelationship to provide for movement of the pull arms relative to theboat through limited arcs of rotation about axes of rotation which areparallel to the axes of the said float supporting spars, a hydrofoilsupporting spar mounted at the upper side of the boat forrotative'movement between the float supporting spars and in parallelrelation therewith, a pair of hydrofoil units secured to opposite endsof the hydrofoil supporting spar at either side of the boat in closelyspaced relation to the said floats, each of said hydrofoil unitsincluding vertically disposed spaced apart struts extending int-o thebody of water and a hydrofoil element pivotally supported between thelower extremities of the struts, each of said hydrofoil devicesincluding control rod means connected between the hydrofoil element andan adjacent pull arm to provide for varying the position of thehydrofoil element in accordance with a change in position of arespective float to which the hydrofoil is connected.

8. A structure according to claim 7 in which the hydrofoil supportingspar is rotatable about a horizontal axis of rotation to provide forswinging the hydrofoil units rearwardly and upwardly out of said body ofwater into a non-operative position.

9. A structure according to claim 7 in which the hydrofoil supportingspar is rotatable about a horizontal axis of rotation to provide forswinging the hydrofoil units rearwardly and upwardly out of said body ofwater into a non-operative position, an operating handle secured to thesaid hydrofoil supporting spar and means for clamping the operatinghandle in a fixed position relative to the upper side of the watercraftto normally maintain the hydrofoils in a submerged position in the bodyof water.

10. A structure according to claim 7 in which the hydrofoil supportingspar is rotatable about a horizontal axis of rotation to provide forswinging the hydrofoil units rearwardly and upwardly out of said body ofwater into a non-operative position and locking means for holding theoperating handle in a raised position.

11. A structure according to claim 1 in which the float members areprovided with laterally extending vanes.

12. A structure according to claim 1 in which the transverse control rodmay be locked to the forward float supporting spar.

13. An apparatus of the class described comprising in combination awatercraft supported in a body of water, float supporting means solidlysecured to the watercraft and projecting transversely outwardly fromeither side thereof, a pair of float members, pull arms projectingdownwardly and rearwardly relative to the float supporting means, saidpull arms hingedly connecting the float members to the float supportingmeans in spaced relation to the watercraft in said water and hydrofoilmeans independently connected to the watercraft and including hydrofoilelements operatively connected to the pull arms and movable therewith,and additional hydrofoil means secured at the stern of the watercraftfor cooperating with the independently connected hydrofoil means topromote stabilization of the watercraft when in motion.

14. An apparatus of the class described comprising in combination awatercraft supported in a body of water, float supporting means solidlysecured to the Watercraft and projecting transversely outwardly fromeither side thereof, a pair of float members, pull arms projectingdownwardly and rearwardly relative to the float supporting means, saidpull arms hingedly connecting the float members to the float supportingmeans in spaced relation to the watercraft in said water and hydrofoilmeans independently connected to the watercraft and including hydrofoilelements operatively connected to the pull arms and movable therewith,and said pull arms and respective float members having stop elementsconnected therebetween to limit change in angularity of the pull armsrelative to their respective floats.

15. An apparatus of the class described comprising in combination awatercraft supported in a body of water, float supporting means solidlysecured to the watercraft and projecting transversely outwardly fromeither side thereof, a pair of float members, pull arms projectingdownwardly and rearwardly relative to the float supporting means, saidpull arms hingedly connecting the float members to the float supportingmeans in spaced relation to the watercraft in said water and hydrofoilmeans independently connected to the watercraft and including hydrofoilelements operatively connected to the pull arms and movable therewith,and said float members and their respective pull arms having connectedtherebetween damping devices for resisting rate of change of angulari'tyof the pull arms relative to their respective floats when the watercraftis moving through the said body of water.

References Cited by the Examiner UNITED STATES PATENTS 10/1945 Hookl1466.5 6/1957 Hook 114-665

1. AN APPARATUS OF THE CLASS DESCRIBED COMPRISING IN COMBINATION A WATERCRAFT SUPPORTED IN A BODY OF WATER, FLOAT SUPPORTING MEANS SOLIDLY SECURED TO THE WATERCRAFT AND PROJECTING TRANSVERSELY OUTWARDLY FROM EITHER SIDE THEREOF, A PAIR OF FLOAT MEMBERS, PULL ARMS PROJECTING DOWNWARDLY AND REARWARDLY RELATIVE TO THE FLOAT SUPPORTING MEANS, SAID PULL ARMS HINGEDLY CONNECTING THE FLOAT MEMBERS TO THE FLOAT SUPPORTING MEANS IN SPACED RELATION TO THE WATERCRAFT IN SAID WATER AND HYDROFOIL MEANS INDEPENDENTLY CONNECTED TO THE WATERCRAFT AND INCLUDING HYDROFOIL ELEMENTS OPERATIVELY CONNECTED TO THE PULL ARMS AND MOVABLE THEREWITH. 